Liquid crystal display devices usually have a combination of a liquid crystal and a retardation film. Retardation films obtained by converting a polycarbonate resin, a cyclic olefin-based polymer resin, or the like into a film and further stretching the film are known (see, for example, JP-A 7-256749 and JP-A 5-2108). Regrettably, however, raw material resins of such films are expensive. Therefore, development of retardation films made of inexpensive plastic materials has been demanded.
For example, JP-A 60-24502 discloses a phase retardation plate made of a polyolefin resin. According to this document, this phase retardation plate is produced by drawing a resin extruded through an outlet of a T-die while cooling it so that the resin will be stretched to a certain degree. However, films obtained by such a method comprising stretching uniaxially in the longitudinal direction are not suited as retardation film because they have retardation unevenness due to uneven orientation in the film width direction or have thickness unevenness in the width direction.